EFFECTS OF BASIC FIBROBLAST GROWTH-FACTOR (BFGF) ON BONE-FORMATION INGROWING RATS

The effects of basic fibroblast growth factor (bFGF) administered intr avenously at dosages of 0.1 and 0.3 mg/kg per day for 7 days to growin g rats are reported. Static and dynamic histomorphometry techniques we re applied to the microradiographs and undecalcified ground sections o f the proximal tibiae and tibial shafts. The bone histomorphometric an alyses in the proximal tibia revealed that 0.1 mg/kg per day of bFGF i ncreased longitudinal growth rate, cartilage cell production rate, and metaphyseal bone area. In the tibial shaft, the endocortical mineral apposition and bone formation rates, total bone area, total osteoid ar ea, and medullary bone area were increased, but the periosteal mineral apposition and bone formation rates were depressed. Two weeks after t he cessation of treatment, the increased osteoid bone on the endocorti cal surface and in the marrow cavity was completely calcified, and the total mineralized area in the tibial shaft was significantly increase d. The rats given 0.3 mg of bFGF/kg per day showed retarded weight gai n, defective calcification at the growth plate metaphyseal junction, a nd on the endocortical surface. The growth plate width was increased, and the longitudinal growth rate, cartilage cell production rate, endo cortical labeled surface, and bone formation rate were decreased. Two weeks after the cessation of treatment, these changes were almost reve rsed, and the longitudinal growth rate and cartilage cell production r ate were increased as rebound phenomena. These results suggest that a low dose (0.1 mg/kg per day) of bFGF stimulates endosteal and endochon dral bone formation and depresses periosteal bone formation in growing rats.